Nominal Plan Research Articles

Visualization of a variety of possible dosimetric outcomes in radiation therapy using dose-volume histogram bands

PurposeDose-volume histograms (DVH) are the most common tool used in the appraisal of the quality of a clinical treatment plan. However, when delivery uncertainties are present, the DVH may not always accurately describe the dose distribution actually delivered to the patient. We present a method, based on DVH formalism, to visualize the variability in the expected dosimetric outcome of a treatment plan. MethodsFor a case of chordoma of the cervical spine, we compared 2 intensity modulated proton therapy plans. Treatment plan A was optimized based on dosimetric objectives alone (ie, desired target coverage, normal tissue tolerance). Plan B was created employing a published probabilistic optimization method that considered the uncertainties in patient setup and proton range in tissue. Dose distributions and DVH for both plans were calculated for the nominal delivery scenario, as well as for scenarios representing deviations from the nominal setup, and a systematic error in the estimate of range in tissue. The histograms from various scenarios were combined to create DVH bands to illustrate possible deviations from the nominal plan for the expected magnitude of setup and range errors. ResultsIn the nominal scenario, the DVH from plan A showed superior dose coverage, higher dose homogeneity within the target, and improved sparing of the adjacent critical structure. However, when the dose distributions and DVH from plans A and B were recalculated for different error scenarios (eg, proton range underestimation by 3 mm), the plan quality, reflected by DVH, deteriorated significantly for plan A, while plan B was only minimally affected. In the DVH-band representation, plan A produced wider bands, reflecting its higher vulnerability to delivery errors, and uncertainty in the dosimetric outcome. ConclusionsThe results illustrate that comparison of DVH for the nominal scenario alone does not provide any information about the relative sensitivity of dosimetric outcome to delivery uncertainties. Thus, such comparison may be misleading and may result in the selection of an inferior plan for delivery to a patient. A better-informed decision can be made if additional information about possible dosimetric variability is presented; for example, in the form of DVH bands.

SU-E-T-619: Dose Evaluation Tool for Proton Patch Field Irradiation

Purpose: Evaluate the tumor coverage and dose to organs at risk (OAR) from proton patch field irradiation using over‐irradiate and under‐irradiate modes. Methods: Proton patch field configuration is a powerful treatment planning tool used in proton therapy to spare OAR. In this beam arrangement a shoot through beam is used to irradiate a large portion of the tumor and one or more patching beams are used to treat rest of the tumor. The patching beam is distally stopped at the lateral edge of the shoot‐ through beam. For such complex beam arrangements a treatment plan done with nominal uncertainties may not be adequate to assess tumor coverage and risk to critical structures. The beam range and patient density uncertainty increase or decrease penetration of a proton beam and position uncertainty expands or contracts the irradiation area by shifting aperture and compensator during treatment delivery. In addition to nominal plan, we used the over‐ and under‐irradiation mode available in our treatment planning system to simulate two extreme circumstances during the treatment delivery. The nominal, over‐irradiate and under‐irradiate plan are used to evaluate tumor coverage and estimate the dose to OAR with the patch field irradiation. Results: In proton patch field irradiation the uncertainties can adversely affect tumor coverage and the OAR. Over‐irradiate and under‐ irradiate mode create dose distributions under extreme but likely coincidence of uncertainties. Using these dose distributions in conjunction with nominal dose distribution can help us evaluate a plan more realistically, and rethink the dose constrains on critical structures. Conclusions: In addition to nominal dose calculation, the over‐irradiate and under‐irradiate mode of dose calculation should be used to evaluate complex proton plans, especially those involving patch fields.

(A219) Development of a Hospital Disaster Plan for Countries with Limited Resources

The Chris Hani Baragwanath Hospital (CHBH) in South Africa is the largest in the world, with 2,900 beds. Its trauma unit boasts 15 resuscitation bays, while the triage area has space for 40 stretchers. There are 5,000 trauma resuscitations performed yearly, out of 50,000 patients seen in the Trauma Emergency Department. There is an eight-bed Trauma Intensive Care Unit (ICU) and a 56-bed Trauma Ward. There also are 25 stepdown beds, 70 outlying beds, a six-bed Burn ICU, 20-bed ward, and a 24-bed shortstay ward. There are about 80 resuscitations and 70 trauma emergency operations weekly. However, the hospital is severely limited in financial and human resources, with only 2–3 interns, two registrars, and one trauma consultant on-call. The hospital is at > 130% bed occupancy. The CHBH was designated as the main disaster hospital for the 2010 FIFA World Cup, due to its proximity to the 96,000-seat Soccer City. Nominal disaster plans existed, but there were no resources, preparations, or knowledge, as was the case with most other government hospitals. The Trauma Directorate developed a new plan for the World Cup, future mass-casualty incidents at CHBH, and for other resource limited hospitals. The plans are centered on four critical issues: (1) preparedness of hospital structure and staff; (2) dissemination of the plan; (3) disaster training; and (4) the development of “Disaster Bags” for 350 casualties A free disaster course trained > 400 staff members on in-hospital triage and trauma management. All hospital staff were allocated specific functions in case of disasters. This is the first time the CHBH has had an integrated disaster plan, with separate equipment allocation, through private funding, and involving all disciplines.

Poster — Thur Eve — 39: Dosimetric Evaluation of Bulk Electron Density Based Treatment Planning in IMRT Head and Neck Patients: Can It Be Used for MRI‐Based Planning?

One limitation of using MRI alone for radiation planning is the lack of electron density for dose calculation. We evaluated the dosimetric accuracy of using bulk density overrides as a substitute for CT‐derived densities in IMRT treatment planning for head and neck cancer. Ten clinically‐approved, CT‐based treatment plans were used for this study. Three dose distributions were calculated for each treatment plan. The first calculation used CT‐derived density as a basis for heterogeneity correction. The second calculation assumed a homogeneous patient density of 1 g/cm3. For the third dose calculation we contoured bones and air cavities and assigned them a uniform density of 1.5 g/cm3 and 0 g/cm3, respectively. The remaining tissue was assigned a density of 1 g/cm3. All three calculations utilized identical beam parameters (angles, segments and MUs). Actual MR images were not used for contouring to avoid effects of gradient distortion and volumetric uncertainties associated with them. All calculations were done using the Collapsed Cone Superposition algorithm in the Pinnacle3 treatment planning system. Our results show that the assignment of bulk density to bones and air cavities was a feasible approach to IMRT treatment planning for head and neck patients. In almost all cases, the dosimetric results were within 2% of the treatment plans based on CT‐derived density. This method may overcome the lack of electron density information in MR‐based planning. The use of homogeneous geometry, while simpler and less time consuming, resulted in unacceptably high errors in the dose distribution compared to the nominal plan. This research project is supported by Philips Medical Systems.

SU‐FF‐T‐94: Dosimetric Evaluation of the Setup and Breathing Motion Effect for Modulated Electron Radiation Therapy of Breast Cancer

Purpose: In conventional photon breast therapy, the effect of setup and breathing motion is accounted for by adding a margin to the clinical target volume (CTV). In modulated electron radiation therapy (MERT), since the electron beams can be arranged nearly along the direction of the organ motion, the effect of breathing motion is greatly reduced. This work is aimed to estimate the dosimetric changes caused by setup and breathing motion for MERT of breast cancer. Method and Materials: Monte Carlo (MC) based inverse treatment planning was used based on the CT data of a breast phantom. The dosimetric accuracy of the MERT delivery using the Siemens photon MLC (pMLC) was verified previously. In this work, five Monte Carlo calculated plans were compared with different static displacements (along the beam direction) of the phantom from its normal position, i.e. ±1cm, ±0.5cm and 0cm. Comparisons were performed in terms of 2D isodose distributions, dose‐volume histograms (DVHs), minimum dose (Dmin), mean dose (Dmean) and maximum dose (Dmax). Results: For ±1cm target displacements, dose differences from the nominal plan (without target motion) are relatively large in both 2D dose distributions and DVHs. For example, the difference in Dmean for this case is about 3.4%, indicating a visible target dose reduction. For ±0.5cm target displacements, a minor difference is seen for the 90% isodose lines, and the difference in Dmean is less than 2%. The integrated dose distributions remain unchanged, indicating the effect of breathing motion on the dose coverage of the target is ignorable. Conclusions: Due to the relatively small SSDs used for pMLC‐based MERT the effect of patient setup may become significant (displacement >0.5cm). Breathing motion has little effect for en‐face electron irradiation. The magnitude of the setup effect can be estimated with the inverse‐square relationship with an accurately determined “effective” SSD.

An adaptive drug delivery design using neural networks for effective treatment of infectious diseases: A simulation study

An adaptive drug delivery design is presented in this paper using neural networks for effective treatment of infectious diseases. The generic mathematical model used describes the coupled evolution of concentration of pathogens, plasma cells, antibodies and a numerical value that indicates the relative characteristic of a damaged organ due to the disease under the influence of external drugs. From a system theoretic point of view, the external drugs can be interpreted as control inputs, which can be designed based on control theoretic concepts. In this study, assuming a set of nominal parameters in the mathematical model, first a nonlinear controller (drug administration) is designed based on the principle of dynamic inversion. This nominal drug administration plan was found to be effective in curing “nominal model patients” (patients whose immunological dynamics conform to the mathematical model used for the control design exactly. However, it was found to be ineffective in curing “realistic model patients” (patients whose immunological dynamics may have off-nominal parameter values and possibly unwanted inputs) in general. Hence, to make the drug delivery dosage design more effective for realistic model patients, a model-following adaptive control design is carried out next by taking the help of neural networks, that are trained online. Simulation studies indicate that the adaptive controller proposed in this paper holds promise in killing the invading pathogens and healing the damaged organ even in the presence of parameter uncertainties and continued pathogen attack. Note that the computational requirements for computing the control are very minimal and all associated computations (including the training of neural networks) can be carried out online. However it assumes that the required diagnosis process can be carried out at a sufficient faster rate so that all the states are available for control computation.

Control of a climbing robot using real-time convex optimization

This paper presents a controller for a free-climbing robot called Cartesian Force Convex control. This controller computes in real-time control inputs that will move a robot safely along a nominal plan by using a convex optimization technique based on an LP solver to compute torques to joint motors. For the LP solution, a cost function is chosen that increases robustness by weighting tracking performance of the robot’s body against the margins in the constraint variables (e.g. proximity of the contact forces to their friction cone limits). The constraints are formulated to characterize the climbing problem and include both static and dynamic limits. The effectiveness of this controller is demonstrated both with simulations and hardware experiments.

Imaging Order Scheduling of an Earth Observation Satellite

This paper presents the research and development of an imaging order scheduler for FORMOSAT-2, an Earth observation satellite taking images of ocean and landmass in the vicinity of Taiwan according to customers' requests. The quality of satellite image pictures depends heavily on the posture and position of the spacecraft as well as on the weather condition of the target area when taking the images. The satellite imaging order scheduler considers current and future weather conditions to provide an imaging plan that satisfies customer requirements with quality imaging pictures. The satellite imaging order scheduling problem is formulated as a stochastic integer programming problem. We adopt the rolling horizon approach to solve this problem. A nominal plan is generated based on the forecast weather conditions. This nominal plan is adjusted with the updated information during its execution. Lagrangian relaxation is used to solve for a nominal imaging plan. Numerical results indicate that our imaging order scheduler is effective and efficient to generate good imaging plans for realistic problems. We also conduct experiments to further explore the algorithmic features. Our analysis of variance (ANOVA) study concludes that the performance of our solution algorithm significantly depends on the number of jobs, as well as the rewards of order completion. However, the effect caused by weather conditions is not obvious.

Image-guided adaptive radiation therapy (IGART): Radiobiological and dose escalation considerations for localized carcinoma of the prostate

The goal of this work was to evaluate the efficacy of various image-guided adaptive radiation therapy (IGART) techniques to deliver and escalate dose to the prostate in the presence of geometric uncertainties. Five prostate patients with 15-16 treatment CT studies each were retrospectively analyzed. All patients were planned with an 18 MV, six-field conformal technique with a 10 mm margin size and an initial prescription of 70 Gy in 35 fractions. The adaptive strategy employed in this work for patient-specific dose escalation was to increase the prescription dose in 2 Gy-per-fraction increments until the rectum normal tissue complication probability (NTCP) reached a level equal to that of the nominal plan NTCP (i.e., iso-NTCP dose escalation). The various target localization techniques simulated were: (1) daily laser-guided alignment to skin tattoo marks that represents treatment without image-guidance, (2) alignment to bony landmarks with daily portal images, and (3) alignment to the clinical target volume (CTV) with daily CT images. Techniques (1) and (3) were resimulated with a reduced margin size of 5 mm to investigate further dose escalation. When delivering the original clinical prescription dose of 70 Gy in 35 fractions, the "CTV registration" technique yielded the highest tumor control probability (TCP) most frequently, followed by the "bone registration" and "tattoo registration" techniques. However, the differences in TCP among the three techniques were minor when the margin size was 10 mm (⩽1.1%). Reducing the margin size to 5 mm significantly degraded the TCP values of the "tattoo registration" technique in two of the five patients, where a large difference was found compared to the other techniques (⩽11.8%). The "CTV registration" technique, however, did maintain similar TCP values compared to their 10 mm margin counterpart. In terms of normal tissue sparing, the technique producing the lowest NTCP varied from patient to patient. Reducing the margin size seemed the only sure way to reduce the NTCP significantly, irrespective of the IGART technique employed. In escalating the dose with the iso-NTCP constraint, the largest average gain in dose was observed with the "tattoo registration" technique, followed by the "CTV registration" and "bone registration" techniques. This is attributed to the fact that in three of the five patients, the "tattoo registration" technique yielded the lowest NTCP, hence a greater window of opportunity to escalate the dose was possible with this technique. However, the variation among the five patients was also largest with the "tattoo registration" technique where, in the case of one patient, the required dose actually needed to be below the original prescription dose of 70 Gy to satisfy the iso-NTCP constraint. This was not the case with the "CTV registration" technique where positive and similar dose escalation was allowed on all five patients. Based on these data, an attractive dose escalation strategy may be to implement the "CTV registration" technique (for consistent dosimetric coverage) for daily target localization in combination with a margin reduction (for increased normal tissue sparing).

Effect of patient setup errors on simultaneously integrated boost head and neck IMRT treatment plans

The purpose of this study is to determine dose delivery errors that could result from random and systematic setup errors for head-and-neck patients treated using the simultaneous integrated boost (SIB)-intensity-modulated radiation therapy (IMRT) technique. Twenty-four patients who participated in an intramural Phase I/II parotid-sparing IMRT dose-escalation protocol using the SIB treatment technique had their dose distributions reevaluated to assess the impact of random and systematic setup errors. The dosimetric effect of random setup error was simulated by convolving the two-dimensional fluence distribution of each beam with the random setup error probability density distribution. Random setup errors of sigma = 1, 3, and 5 mm were simulated. Systematic setup errors were simulated by randomly shifting the patient isocenter along each of the three Cartesian axes, with each shift selected from a normal distribution. Systematic setup error distributions with Sigma = 1.5 and 3.0 mm along each axis were simulated. Combined systematic and random setup errors were simulated for sigma = Sigma = 1.5 and 3.0 mm along each axis. For each dose calculation, the gross tumor volume (GTV) received by 98% of the volume (D(98)), clinical target volume (CTV) D(90), nodes D(90), cord D(2), and parotid D(50) and parotid mean dose were evaluated with respect to the plan used for treatment for the structure dose and for an effective planning target volume (PTV) with a 3-mm margin. Simultaneous integrated boost-IMRT head-and-neck treatment plans were found to be less sensitive to random setup errors than to systematic setup errors. For random-only errors, errors exceeded 3% only when the random setup error sigma exceeded 3 mm. Simulated systematic setup errors with Sigma = 1.5 mm resulted in approximately 10% of plan having more than a 3% dose error, whereas a Sigma = 3.0 mm resulted in half of the plans having more than a 3% dose error and 28% with a 5% dose error. Combined random and systematic dose errors with sigma = Sigma = 3.0 mm resulted in more than 50% of plans having at least a 3% dose error and 38% of the plans having at least a 5% dose error. Evaluation with respect to a 3-mm expanded PTV reduced the observed dose deviations greater than 5% for the sigma = Sigma = 3.0 mm simulations to 5.4% of the plans simulated. Head-and-neck SIB-IMRT dosimetric accuracy would benefit from methods to reduce patient systematic setup errors. When GTV, CTV, or nodal volumes are used for dose evaluation, plans simulated including the effects of random and systematic errors deviate substantially from the nominal plan. The use of PTVs for dose evaluation in the nominal plan improves agreement with evaluated GTV, CTV, and nodal dose values under simulated setup errors. PTV concepts should be used for SIB-IMRT head-and-neck squamous cell carcinoma patients, although the size of the margins may be less than those used with three-dimensional conformal radiation therapy.

MIPAS-ENVISAT limb-sounding measurements: trade-off study for improvement of horizontal resolution

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a limb-scanning spectrometer that has operated onboard the Environmental Satellite since the end of March 2002. Common features of limb-scanning experiments are both high vertical resolution and poor horizontal resolution. We exploit the two-dimensional geo-fit retrieval approach [Appl. Opt. 40, 1872-1875 (2001)] to investigate the possibility of improving the horizontal resolution of MIPAS measurements. Two different strategies are considered for this purpose, one exploiting the possibility (offered by the geo-fit analysis method) for an arbitrary definition of the retrieval grid, the other based on the possibility of saving measurement time by degrading the spectral resolution of the interferometer. The performances of the two strategies are compared in terms of the trade-off between the attained horizontal resolution and the retrieval precision. We find that for ozone it is possible to improve by a factor of 2 the horizontal resolution, which in the nominal measurement plan is approximately 530 km. This improvement corresponds to a degradation of the retrieval precision, which on average varies from a factor of 1.4 to 2.5, depending on the adopted spectral resolution.

ESTIMATING POPULATION TRENDS WITH A LINEAR MODEL

Abstract We describe a simple and robust method for estimating trends in population size. The method may be used with Breeding Bird Survey data, aerial surveys, point counts, or any other program of repeated surveys at permanent locations. Surveys need not be made at each location during each survey period. The method differs from most existing methods in being design based, rather than model based. The only assumptions are that the nominal sampling plan is followed and that sample size is large enough for use of the t-distribution. Simulations based on two bird data sets from natural populations showed that the point estimate produced by the linear model was essentially unbiased even when counts varied substantially and 25% of the complete data set was missing. The estimating-equation approach, often used to analyze Breeding Bird Survey data, performed similarly on one data set but had substantial bias on the second data set, in which counts were highly variable. The advantages of the linear model are it...

A compliant controller dynamically updating the compliance center by contact localization

This paper presents a compliant control method for insertion of complex objects with concavities. Most work on robot assembly using compliant motion control schemes focuses on overcoming jamming conditions for simple peg-in-hole problems, and cannot be used for complex shapes frequently encountered in assembly applications. When an object is being inserted to a hole or slot with a small clearance, a contact path is issued to compensate for uncertainties. When the object shape is complex, however, the contact state changes several times and severely, making compliant control difficult. The algorithm presented here is capable of generating satisfactory compliant motion control in spite of changing contact states. During the execution of a nominal motion plan, it computes the actual position of the contact point from the force/torque sensor reading using a contact localization algorithm. It then dynamically updates the center for compliance to the computed contact point, and minimize the chance of jamming and unwanted collisions. The control scheme has been implemented on hardware and tested on the task of inserting a T-shape into a C-shape involving a very tight tolerance. The insertion motion was accomplished by a sequence of 2 translational and 1 rotational compliant motions, and successfully executed by the proposed compliant motion controller.

Assembly of complex shaped objects: A stiffness control with contact localization

This paper presents a compliant control method for insertion of complex objects with concavities. The control algorithm presented here is capable of generating satisfactory compliant motion control in spite of changing contact states. During the execution of a nominal motion plan, it computes the actual position of the contact point from the force/torque sensor reading using a contact localization algorithm. It then dynamically updates the center of compliance to the computed contact point, and minimizes the chance of jamming and unwanted collisions. The control scheme has been implemented on hardware and tested on the task of inserting a T-shaped object into a C-shaped cavity with a very tight tolerance. The insertion motion, which involves a sequence of 2 translational and 1 rotational compliant motions, was successfully executed by the proposed compliant motion controller.

A method of incorporating organ motion uncertainties into three-dimensional conformal treatment plans

Purpose : We describe a method of incorporating organ motion into three-dimensional (3D) conformal treatment plans, which predict the effect of organ motion on the calculated dose to both the clinical target volume (CTV) and nontarget organs. Methods and Materials : The method is based on measurements of organ motion by means of multiple computed tomography (CT) scans from a group of “reference” patients, in which the data consist of previously drawn contours of the target and nontarget organs. A computer program records the differences in contour position and shape that occurs between scans in the reference data, and according to those differences adjusts the contours and dose calculation points of a study” patient currently being planned, thus simulating organ motion. Dose-volume histograms (DVHs) are accumulated, and the process is repeated over the set of reference patient scans, resulting in a set of treatment plans that are ranked according to a dose-based endpoint. Two plans are selected corresponding to specified lower and upper confidence limits in the endpoint, and the DVHs from these plans are displayed for comparison with the DVHs from the nominal plan in the absence of motion. Results | As an example of the method's use, it is applied to a 6-field conformal treatment plan for prostate cancer. Confidence limit DVHs of the CTV and rectal wall (in which the plans were ranked by probabilities for tumor control and normal tissue complication, respectively) are presented and compared to those from the nominal plan. Conclusion : The method provides a means of estimating the uncertainty in dose delivered by a treatment plan when organ motion is present. It is generally applicable to any treatment site for which data in the form of multiple CT scans are available, and can be extended to include other treatment uncertainties such as variation in patient positioning.

Optimal and suboptimal motion planning for collision avoidance of mobile robots in non-stationary environments

An optimal control formulation of the problem of collision avoidance of mobile robots moving in terrains containingmoving obstacles is presented. A dynamic model of the mobile robot and the dynamic constraints are derived. Collision avoidance is guaranteed if the minimum distance between the robot and the objects is nonzero. A nominal trajectory is assumed to be known from off-line planning. The main idea is to change the velocity along the nominal trajectory so that collisions are avoided. Furthermore, time consistency with the nominal plan is desirable. Two solutions are obtained: (1) A numerical solution of the optimization problem and a perturbation type of control to update the optimal plan and (2) A computationally efficient method giving near optimal solutions. Simulation results verify the value of the proposed strategies and allow for comparisons.

Simulating physical interactions between an articulated mobile vehicle and a terrain

This paper deals with the problem of planning the motion of a complex land vehicle moving in a natural environment. The contribution presented here is a motion generator which predicts the dynamic behaviour of the vehicle when executing a given nominal motion plan. This plan is expressed in terms of a channel that must be followed and of a set of intermediate subgoals that must be reached. Solving this motion generation problem requires to explicitly reason about the geometric and the physical aspects of the movements that the vehicle has to execute. In our approach, this is done by using two basic constructions derived from the concept of physical model: the ‘generalized obstacles’ are used to physically guide the movements of the vehicle using an explicit model of the vehicle-terrain interactions, and the ‘physical targets’ are used to map the strategic information onto our physical representation of the world and to introduce the force feedback gestural control.

Physical simulation of land vehicles with obstacle avoidance and various terrain interactions

AbstractProgramming the motions of an autonomous planetary robot moving in an hostile and hazardous environment is a complex task which requires both the construction of nominal motion plans and the anticipation as far as possible of the effects of the interactions existing between the vehicle and the terrain. In this paper we show how physical models and dynamic simulation tools can be used for amending and completing a nominal motion plan provided by a classical geometrical path planner. The purpose of our physical modeller‐simulator is to anticipate the dynamic behaviour of the vehicle while executing the nominal motion plan. Then the obtained simulation results can be used to assess and optimize the nominal motion plan. In the first part, we outline the physical models that have been used for modelling the different types of vehicle, of terrain and of vehicle‐surface interactions. Then we formulate the motion planning problem through the definition of two basic abstract constructions derived from physical model: the concept of generalized obstacle and the concept of physical target. We show with various examples how it is possible, when using this method, to solve the locomotion problem and the obstacle avoidance problem simultaneously and, furthermore, to provide the human operator with a true force feedback gestural control over the simulated robot.

Commentary—Approaches to Promotion Evaluation: A Practitioner's Viewpoint

As a marketing practitioner, I applaud Messrs. Abraham and Lodish and Messrs. Blattberg and Levin for attempting to unravel the effects of promotional actions, especially those directed at the retail trade. Both papers demonstrate a keen awareness of the “messy” problems confronting practitioners, such as gaps in companies' internal records, numerous deviations from nominal promotional plans, inadequacies in the common sources of competitive sales data, and the confounding of various merchandising actions.

Inertial Confinement Fusion Development Options: Facility Characteristics and Schedules from a Reactor Physics Viewpoint

The pulsed, localized fusion source in inertial confinement fusion (ICF) permits scale-down of reactor dimensions and fusion yield in development facilities while still maintaining full-scale reactor surface and volume energy loads. Hence, the power and geometric scale of ICF development facilities can be much smaller than comparable magnetic fusion facilities. The power is reduced by reducing both the pulse rate and the target gain; however, full gain and pulse rate experiments of limited duration will be possible. At least three engineering facilities will be required for the development of heavy-ion beam or short wavelength laser driven fusion power. The design and construction times required for large facilities produce a nominal plan with a demonstration (DEMO) plant operating around the year 2018, and a crash plan with DEMO operation in 2009. Fusion breeder development is expected to follow a similar time line, except that a crash (option-limited) plan could succeed as early as the turn of the century.